The timing of breast cancer surgery during the menstrual cycle.

A number of recent studies have suggested that survival among premenopausal women after primary treatment of breast cancer may be affected by the estimated hormonal milieu at the time of surgery, especially in those with axillary lymph node metastases. The concept has created considerable controversy and has resulted in the publication of many negative reports. However, several biological mechanisms have been suggested for the observed survival advantage. These include cyclical patterns of immune function, as well as cell division and cell death, that correlate with hormonal fluctuations of the menstrual cycle. Comparisons among studies of timing have been complicated by differences in menstrual cycle divisions, variability in the sources of study populations, limited availability of menstrual history data, and changes over the past 2 decades in primary and adjuvant breast cancer therapy. Several recent publications have been enhanced by the availability of serum collected at the time of surgery that enables accurate measurement of the hormonal milieu. In these studies, the likelihood of misclassification by menstrual cycle phase is reduced, and dependence on recalled menstrual history is eliminated. High progesterone levels have been associated with improved survival. These findings have encouraged some to suggest that perioperative administration of progesterone or tamoxifen (Nolvadex) may provide a preventive avenue comparable to scheduling surgery during the luteal phase. Further multidisciplinary studies are needed, however, to clarify the influence of the naturally occurring or medically induced hormonal milieu at the time of breast cancer surgery on survival in premenopausal women.